Understanding the Risks: Are There Any Downsides to Taking NAD?

October 6, 2025 •

4 min read

While proponents tout NAD supplements for boosting cellular energy and promoting longevity, studies show that side effects can include nausea, fatigue, and headaches. Understanding these potential risks is crucial for anyone asking: are there any downsides to taking NAD?

Quick Summary

NAD supplements can cause side effects like nausea and fatigue, with different precursors and delivery methods carrying varying risks. Long-term safety data is limited.

Key Points

Common Side Effects: Mild symptoms like nausea, fatigue, headaches, and digestive issues are the most frequently reported downsides of NAD precursors.
Precursor-Specific Issues: Older precursors like niacin are known for causing significant skin flushing, while newer ones like NR and NMN have milder side effect profiles, but can still cause digestive and skin problems.
IV vs. Oral Risks: IV infusions can cause immediate, intense side effects such as chest pressure and nausea due to rapid absorption, whereas oral supplements have a slower, more gradual effect.
Cancer and Inflammation Concerns: A theoretical risk exists that boosting NAD+ could fuel pre-existing cancer cells, although it doesn't cause cancer. Chronic inflammation can also be affected, requiring careful consideration.
Long-Term Safety: Extensive long-term human safety studies on NAD supplementation are still lacking, meaning the long-term consequences are not fully known.
Important Contraindications: Individuals with a history of cancer, severe liver or kidney impairment, and those on specific medications (e.g., blood pressure, insulin) should exercise extreme caution or avoid NAD supplements.

Common Side Effects of NAD Supplements

NAD, or Nicotinamide Adenine Dinucleotide, is a vital coenzyme involved in cellular metabolism and DNA repair. As its levels naturally decline with age, supplements designed to boost NAD+ have gained significant attention. However, both oral supplements and intravenous (IV) therapies can cause side effects. These can vary depending on the specific precursor used, such as Nicotinamide Riboside (NR), Nicotinamide Mononucleotide (NMN), Nicotinamide (NAM), or Nicotinic Acid (niacin).

Oral Supplement Side Effects

Gastrointestinal Upset: Some users report mild issues like nausea, diarrhea, and stomach discomfort, which often subside as the body adjusts.
Headaches and Fatigue: Headaches, fatigue, and brain fog are also commonly reported, especially when starting a new regimen. For some, this fatigue may be temporary as the body adapts to increased metabolic demand.
Flushing and Skin Issues: Nicotinic acid (niacin), one of the older NAD precursors, is well-known for causing uncomfortable skin flushing, itching, and rashes at doses over 50 mg/kg. While newer precursors like NR and NMN are less associated with flushing, skin issues can still occur.

IV Therapy Side Effects

IV administration delivers NAD+ directly into the bloodstream, bypassing the digestive system for more immediate effect. However, this method has its own set of potential side effects, which are often related to the rate of infusion.

Physical Discomfort: Rapid IV infusion can cause immediate and intense effects like chest tightness, pressure, flushing, muscle cramps, and nausea.
Injection Site Reactions: As with any IV treatment, there is a risk of localized irritation, redness, or bruising at the injection site.
Metabolic Response: The intense metabolic surge from IV therapy can sometimes lead to temporary fatigue or irritability as the body adapts.

Significant Health Risks and Concerns

Beyond the mild side effects, there are more serious health risks and contraindications associated with NAD supplementation. Given that NAD affects numerous cellular processes, chronic or high-dose use requires careful consideration, especially for individuals with pre-existing conditions.

Theoretical Cancer Risk

One of the most concerning theoretical risks involves cancer. NAD+ is essential for cell survival and proliferation, and some researchers worry that boosting NAD+ levels could inadvertently fuel cancer cells if they are already present.

Dual-Edged Sword: NAD+ is needed for DNA repair, which theoretically protects against cancer-causing mutations. However, cancer cells are known for their high energy demands and rapid growth, which also relies on NAD+.
Uncertainty: The exact relationship between NAD+ supplementation and cancer is complex and not fully understood. It is strongly advised that individuals with a history of cancer or a high risk consult a healthcare provider before using NAD boosters.

Organ and Metabolic Concerns

Liver Function: High doses of certain precursors, particularly nicotinamide (NAM), have been linked to potential liver toxicity in animal and human studies. Individuals with pre-existing liver conditions, such as cirrhosis or fatty liver disease, should avoid these supplements.
Methylation Disruption: The breakdown of some NAD precursors, like nicotinamide (NAM), consumes methyl groups, potentially disrupting the body's methylation cycle. Chronic disruption of methylation can impact DNA and protein function, though short-term studies with NR showed no significant impact on methylation markers.
Insulin Sensitivity: Some studies have raised concerns that NAD supplements could alter glucose metabolism and potentially decrease insulin sensitivity, which is particularly relevant for individuals with diabetes or metabolic disorders.
Blood Pressure: NAD supplements may influence blood pressure, potentially causing significant drops when combined with blood pressure medication. Those on antihypertensives should exercise caution and consult their physician.

Regulatory and Long-Term Safety Uncertainty

Supplementation with NAD precursors remains a relatively new area of research, particularly concerning long-term human use.

Limited Human Data: While short-term human trials generally suggest NAD precursors are safe and well-tolerated, extensive long-term safety data is lacking. The effects of chronic supplementation are not yet fully understood.
Regulatory Flux: The regulatory landscape is uncertain. For instance, in 2022, the FDA ruled that NMN could no longer be marketed as a dietary supplement because it had been investigated as a drug, leading to sales restrictions.
Animal Study Inconsistencies: While some animal studies show benefits, others have raised red flags. For example, high-dose NR in mice has been linked to glucose intolerance and potential cancer risks, highlighting the need for more human-specific research.

The Spectrum of NAD Supplementation: Risks and Efficacy


NAD Delivery Method	Benefits	Potential Downsides	Who Should Be Cautious?
Oral Precursors (NR, NMN)	Convenient, supports maintenance, generally mild side effects.	Mild GI issues, headaches, fatigue, unclear long-term effects.	Anyone with cancer risk, liver issues, on certain meds.
IV Infusions	Rapid absorption, potential for quicker results.	Infusion-related discomfort (chest pressure, nausea), higher cost, minimal long-term data.	Individuals with heart or kidney issues, pregnant/breastfeeding women.
Nicotinic Acid (Niacin)	Well-studied, lipid-lowering effects at therapeutic doses.	Significant flushing, itching, potential liver issues at high doses.	Anyone sensitive to flushing, liver disease patients.

Is NAD Right for You? A Personalized Approach

Before starting any NAD supplement regimen, it is crucial to consider individual health factors, potential risks, and the limited long-term research. While NAD boosters may offer benefits for some, especially older adults experiencing age-related decline, they are not a magic bullet. A healthy lifestyle, including regular exercise and a balanced diet, remains the cornerstone of maintaining cellular health. Natural sources of NAD precursors, like tryptophan in turkey and niacin in fish, can also be a part of a nutritional strategy.

Ultimately, the decision to take NAD supplementation should be a well-informed one, made in consultation with a qualified healthcare provider who can assess your specific health status and goals. Taking a cautious and evidence-based approach is key to balancing potential benefits with the risks involved.

For more in-depth information, consult research from the National Institutes of Health.(https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9917998/) provides a detailed review of the role of NAD+ in aging and associated disorders. Consulting such resources, alongside professional medical advice, is the most responsible way to approach supplementation..

Frequently Asked Questions

The most common mild side effects include nausea, headaches, diarrhea, and fatigue, which often lessen as the body adjusts to the supplement.

There is no direct evidence that NAD supplements cause cancer. However, since cancer cells have high energy demands, a theoretical risk exists that boosting NAD could potentially fuel pre-existing cancer cells. Individuals with a history of cancer should consult a doctor before supplementing.

Individuals with a history of cancer, severe liver or kidney problems, pregnant or breastfeeding women, and those on certain medications like insulin or blood pressure drugs should avoid or consult a doctor before taking NAD boosters.

Yes, high doses of some precursors, like nicotinamide, have been associated with liver toxicity in some studies. People with pre-existing liver disease are at higher risk and should not take these supplements.

Yes. IV infusions can cause more immediate and intense side effects such as chest pressure, nausea, and flushing, often related to the infusion speed. Oral supplements tend to have milder, slower-onset effects.

No, long-term safety data for NAD supplementation in humans is currently limited. While short-term trials show mild side effects, the consequences of chronic use are not yet fully understood.

Yes, NAD supplements can interact with certain medications, including those for diabetes (e.g., insulin) and blood pressure, potentially causing dangerous drops in blood sugar or blood pressure. Always consult a healthcare provider if you are taking other medications.

Some NAD precursors can consume methyl groups during metabolism, which can potentially disrupt the methylation cycle, impacting cellular function. Short-term studies on NR, however, showed minimal impact on methylation.